Problem: I want to remotely access my computer from untrusted computers like on friends house or at work.
Looking for: Remote desktop software (SSH is out of scope, as it could do commands in the background). Client should work in the browser or have portable binaries. Server should send some soft of 2FA before every connection without a way to remember it, so I could be safe in a case of a keylogger snooping on connection password. Not nessesary, but would be nice to have some sort of rate limiting for the inputs, so it won't be possible for some rubber-ducky style script to open terminal and run command before I could react.
RustDesk sort of fits the bill. It's open-source, has 2FA, can be self-hosted (but not needed), the client runs on anything, but the main issue here is that no amount of workarounds will make an untrusted machine any less untrusted, you're essentially extending the display and input from a dubious machine into your own.
If you're really worried about the security aspect, my suggestion would be to only use your phone as the client, and if you need to do anything more complex, use a Bluetooth keyboard connected to it. There are some foldable keyboards that don't take too much space and are not terrible.
Apache Guacamole might be a good option. "Clientless" (browser-based), supports various mfa, uses ssh/vnc/rdp on the backend.
However, if the data on that machine is sensitive, or if that machine has access to other sensitive things on your network, I'd suggest caution in allowing remote access from untrusted machines on the wider internet.