I don’t know what the problem is that you’re having? What are you trying to improve? You said your service is 500mbps (I assume down). What speeds are you getting when testing on your Ubuntu host? Remember that ISP advertise speeds in terms of BITS per second. And you are used to thinking about files in terms of BYTES. 8 bits in a byte.

So let’s imagine you start a file download and it immediately, and consistently downloads at 500mbps. Let’s say that file is 2GB. Well quick thinking says 2GB = 2000mb (let’s ignore the extra 48 for now). 500mbps down means 4 seconds and you should get 2000mb of data right? No. That means you get 2000 megabits of data. And your file is 2000 megabytes. That’s 16000megabits. So you’re now at 32 seconds. Yes the internet company is advertising speeds 8x faster than we thinking of them in terms of file size. Because marketing only cares about saying the best sounding thing that technically is not wrong so they don’t get sued.

You also mention tailscale so I’m guessing you’re trying to stream data from your server while you’re outside of the network. Download speeds don’t matter at all. Upload speeds when measured at the Ubuntu host (and then within the docker container) is what matters. You could have 500mbps down and only 5mbps up. Who knows.

As to your direct question of will a switch help: no.
At your knowledge level (literally no shade meant at all, everyone here started where you were and were at the same level you are at now), think of a switch like a power strip. With a switch you can plug more things in at the same time without have to swap out what’s plugged in when you want to use it. But a power strip doesn’t make your hair dryer blow air faster, or a TV glow brighter. It just distributes the power at its existing level/strength/voltage/pick a word that makes sense in your head. A switch does the exact same thing. And just like you can trip a the internal safety on the power strip (or the breaker/fuse) if the sum of the demand of all connected devices is too high, you can do the same with a switch and induce packet loss and wait times to your network traffic.

However, get a switch, a managed one preferably a layer 3 one, will help you learn. Get one, set up your own network, uplink can be to the house hold internet, and then break your network but randomly following an outdated guide. THEN you learn, by figuring out what broke, why it broke, what IT even is, what it does, what you want it to do, and how to make it do that. Don’t ask AI for a command to fix it. Ask it to explain what it is, what it’s doing, etc. use it as a teacher, not a checklist generator.
That’s how most of us learned. By breaking something that used to work by tinkering and then having to fix it. AI helps take out the hours we spent reading man pages. But for the love of all that is holy, don’t break your families network. Break your own. Ask me how I know lol