I don’t know about older Surfaces, but for me in a nutshell, H-E-Double hockey sticks on my 1st gen Surface Go. Only install Linux on a Surface if you already own one.
More in-depth, it was usable - it was my main personal on-the-go device for a couple of years. I’d had it since before I used Linux. On mainline, the main stuff worked. With the Linux-Surface kernel, I could get the cameras working. It was always very janky (you had to bridge stuff through GStreamer or some other weird crap rather than using it directly. Don’t remember the specifics), but it worked.
Another annoyance was a hardware issue with the keyboard when it was in your lap: since the keyboard wasn’t very rigid, it would bend a bit while typing or placing your hand on the palm rest, making unwanted mouse clicks
My big problem with the Surface Go, though, was I had chronic issues with power profiles. It never went to sleep quite right, so after closing it a few times, the system would begin to get unstable and I’d just have to do a reboot.
After my initramfs got borked on that during the time_t64 transition (my fault, not the hardware’s; I use Debian Testing and an apt update went awry), I didn’t feel like going back and fixing it, as I was planning on replacing this device with the Thinkpad I write this on anyway.
Ultimately, my opinion (again, just based on using the Go 1, which is a bit newer than the Pro 4) is that it isn’t the best idea. Considering Pro 4s are not expensive on eBay, trying it isn’t the worst idea, but I feel like it’s not worth it, an unfortunate truth considering Surfaces are such unique devices. This isn’t a cheap alternative (the CPU’s not the best from what I can tell), but the Surface fan in me finds the StarLabs StarFighter 12.5-inch enticing considering it’s both very Surface-like and Linux-friendly.
As you want cheap, you might be able to find something to throw LineageOS or postMarketOS on. Honestly, my question for you is how much do you need a tablet specifically? Could a small laptop do?