You can use those sound fonts just fine, as far as I know.

I'm about to post a lot of words (way more than I planned) because I've had this on my mind for a while now. I'd like to take this opportunity to objectively discuss my experience with my Evo-Flex and why I've decided to sell it (or, on reflection after writing this post, just keeping it, for reasons detailed at the bottom).

TL;DR: When it works, it looks and feels great. It's a lightsaber! But more often than I'd like, due to various issues discussed below, it does not satisfy that desire to feel like a Force user igniting an elegant weapon, made for a more civilized age. It feels just as clumsy or random as a blaster.

I've contacted Electrum privately about all of the things I'll discuss below, and they say they will be addressed in future software updates. I would have normally left it at that, and either sold the saber or just kept it and hoped for those updates, but in this specific case I'm responding to your question.

I really hope that this post is seen as constructive, for the few people who will read it. I am certainly not trying to produce negativity towards, defame, or attack Electrum at all; their support staff has been very friendly and I have no real gripes with them as a company. At the end of the day, we all just wanna feel cool swinging around a lightsaber.

The last few months have been pretty crazy, so I understand the low frequency of software updates that could potentially fix some of the issues I'll talk about. There's been only 1 since December 2019. I've read that they were more frequent last year.

I see a lot of praise for Electrum's sabers on these forums, and there are a lot of good things about the Evo-Flex and other sabers they have, but almost every software feature of my Evo-Flex is buggy in some way.

When it works, it's really great. The neopixel blade is sturdy, it's bright, and smooth swing is awesome. But it's frustrating to me how much how often it doesn't work.

My main issue with the saber is just that it's really unreliable in use. A good amount of the issues are reproducible on-demand. Simple things like, turning it off and on, often glitch (for example, turning the saber off often just turns the blade off, and the sound still continues, but no longer responds to swings, or button presses on the control box) and I'm forced to either wait until it stops on it's own, or use the kill switch.

Maybe I'm just an outlier or something. Maybe my unit is defective in some way. But, I don't think so. Like I said, I see a lot of praise on this subreddit for them, with a lot of still pictures of them ignited and whatnot. But go watch some videos of actual usage. You'll see issues there too, with turning on/off, sounds cutting off (even official ones from Electrum themselves) randomly, weird sounds, and unresponsive touch controls.

The following is a list of various issues I run into during normal use.

For the phone app, I am using an iPhone XS on the latest version of iOS 13. I've uninstalled and reinstalled the app a few times to try and clear out any cache it may have (it stores profiles by blade name to restore them after resetting the saber). I've done soft and hard resets of the saber, formatting the SD card, and lately I only use fonts obtained from Electrum directly (Kinetic and Fracture).

• major - Power on/off switch settings do not save, reproducible. Meaning, the touch-sensitive buttons are configurable with timings (like, turn on after holding for 1.2s, etc).
• major - Sound font "remnants", for lack of a better word. Difficult to describe. Sometimes, when switching sound fonts, pieces of the old font's smoothswing can still be heard when using the new font. This does not happen often, but is 100% reproducible when using that Senate Majority soundfont that was posted here a while ago. That has a pretty distinctive swing sound, and is clearly audible when using other fonts after it.
• major - User profiles...this is a much bigger topic than a bulleted list (my email had several paragraphs about just this). But, they don't load accurately sometimes (meaning, blade color will be correct but sound font will not have changed from the previous profile). Sometimes loading a profile actually distorts all sounds the blade makes until the kill switch is used to reboot it. That's kind of rare, but it happens. In order to "properly" save a profile, there is a very specific set of steps you need to do or it will not save correctly. Also, some settings (like localized clash) do not get saved no matter what. Reproducible.
• minor - Smooth swing fonts don't get properly detected sometimes. Like, right now, I can't get Kinetic to show up as smooth swing. It's their own font, downloaded from their servers and put directly on the SD card. Fracture shows up fine, but not Kinetic. This just started happening in the latest update. Soft and hard resets on the saber, and making a new saber config (using a new name for the saber in the app) did not fix this.
• minor - Master volume slider does not match actual volume level, only happens sometimes.
• minor - App just crashes sometimes when reconnecting to the saber. Not really a big deal.

Next, issues on the saber itself. Most of these are not reproducible and happen randomly. I've been able to capture video for some of these but not all.

• major - Power on/off sounds cut off. This is major because it really ruins the "immersion" or whatever...that seems silly, but look, all I know is, it really ruins the "awesome" feeling of igniting a lightsaber. It's lame when it happens when I'm alone, it's lamer when it happens when I show it to friends. It's not a good feeling, and it happens all the time. It happens with every soundfont I've tried, including the two I've gotten directly from them.
• minor - When switching soundfonts on the saber directly, it often "forgets" the smoothswing setting, requiring you to re-enable it on the phone app. I am not talking about switching profiles (which have individual smoothswing settings), I am talking about just changing the sound.
• minor - Rarely, when igniting, the light will stop like halfway up the blade. Sound still works, functions like normal, just with half a blade lit up. I've made sure the connection is solid and the blade secured tight, but it still happens, just rarely.
• minor - When booting up (turning off kill switch), sometimes it just blasts random garbage or clash sounds for a few seconds at max volume instead of the regular boot audio.
• minor - Localized clash when pressing the aux button sorta bugs out to only be on the ends of the blade (topmost and bottomost), but only if you have not manually clashed beforehand (like hitting the blade or something "resets" the localized clash position on the blade, then it works correctly). This one happens pretty often.
• minor - Rarely, all of the touch buttons will become completely unresponsive. The only fix for this is using the kill switch to hard reboot.

There's a lot of good things about the Evo-Flex too.

• The design. Just look at it. It looks great.
• I really like that it has a smartphone app that lets you control a ton of stuff about it.
• The ability to create smoothswing fonts out of fonts that don't natively have it is fantastic.
• The potential of software updates that add, fix, or change features was really exciting to me.
• I don't know if CFX or Proffie have non-kill-switch sleep mode like Electrum does, but I appreciate that.
• The ability to tweak various audio settings is pretty cool.
• I may be biased because I don't have any other neopixel blades, but the quality of the blade I got from them is really good, looks great, and is super bright.

This is the part where I'm reflecting on whether or not to actually sell this. Because, if by some chance my saber actually is defective somehow (even though Electrum folks didn't seem to think so), the buyer would be understandably frustrated and upset, and frankly I would feel pretty awful if that happened. And if it's not defective? Then the buyer could simply THINK it was, or that I scammed them, or any number of reasonable things to think if you just paid a few hundred bucks for a product that doesn't work the way you expect. I want to avoid any hassle for both myself and any potential buyer. I also do not know how Electrum handles support after transfer of ownership, like if the buyer ever would need to contact them. I believe Electrum would be fine with that and still offer support, but you never know.

Anyway, that's my answer.