With heavier services removed, it turns out this site can run on a Raspberry Pi! It’s a bit low in RAM headroom, mainly due to MySQL, but it cut my network and server hardware power usage by about 2/3! Ubuntu 20.04 works quite nicely on it, and I ran into a certbot bug while I was at it. An interesting experience!
Is it RPi 3B or 4B? If it’s the latter one then how much RAM does it have?
It’s a 4; only 1 GiB RAM. I’ve since moved to a VPS.