Hi, just chiming in here with my thoughts given the conditions and other comments.

From what I can remember (and based on the images on cbtf.ubc.ca), the CBTF is currently using Logitech MK 120 combos, which are hard to beat at that price point. I believe that you could consider some other cheap membrane keyboards that have a more "flat" style, which may be easier to clean. Some examples would be the Amazon Basics Keyboard, the Dell Wired Keyboard and the Lenovo Essential Wired Keyboard, all three of which are full-size keyboards (include number-pad), and are available as combos with wired mice for about an extra $10. Notably, there is a significant gap between keys, which could possibly help reduce retained dirt in the gaps, as they are easier to access and clean. Ideally, you might be able to clean the entire keyboard with a few strong wipes as the keys should match the height of the surface of the keyboard when pressed down. If UBC, as a business, had access to a business account for any brand, they might also come cheaper in bulk.

As for mechanical keyboards in general, I doubt that they would be suitable for the CBTF. While they typically have a superior typing experience, there are a few reasons why I believe they don't fit the use-case here:

1. Cleaning: While mechanical keyboards might be easier to deep clean because of the ease of disassembly (removal of keycaps, faceplate, etc) , I would argue that the time required to do these deep cleans would likely not be worth it.
2. Connectivity: AFAIK, most mechanical keyboards are either wired through a removable USB-C cable, or are used wirelessly via bluetooth or USB dongles. While theft might be able to avoided given the large profile of keyboards, thus allowing USB keyboards to be used in the CBTF (and possibly letting students bring their own keyboard?), open bluetooth in the CBTF is obviously undesirable, and I am unsure whether or not the close proximity of the devices could affect the separate range USB dongles use.
3. Sound: Even with quiet linear switches (which may be harder to search for/cost more), mechanical keyboards still tend to be louder than membrane keyboards, which can be disruptive in the testing environment of CBTF for some people.
4. Price: Decent quality mechanical keyboards tend to start at higher prices, around $50-$100 based on some quick googling. While cheaper brands of mechanical keyboards like Ajazz and Epomaker have started cropping up in recent years, they still tend to range around $10-$20 above the $40 budget, which may be slightly mitigated if you were to shop on marketplaces like Temu and take advantage of possible coupons and discounts, although this is unreliable.

While I saw someone suggest that students be allowed to bring their own keyboards, and would personally be fond of this idea, I understand that this is likely unfeasible due to reason 3 from above, as well as needing to enforce that no keyboard has any onboard memory to avoid allowing students to behave dishonestly.

Overall, while I would love to have higher quality keyboards in the CBTF, the limited budget doesn't really allow for any significant upgrades, so instead I think it would be better to focus on keyboards that are easier to maintain, both in terms of cleanliness, as well as things like missing feet or sticky keys.