My solution was to use a machine that's similar to what Googlers use. Even though devs at Google use 64GB RAM and Xeon chips, I've found that an Eight-core Ryzen chip at 4GHz with 32GB of RAM on Linux makes Gmail fly. I can run and work with Mutt efficiently on a Raspberry Pi, but I need an desktop machine to make Gmail work fast. We live in interesting times.
Gmail is unusable in my 2012 MacBook Pro. I wonder how Gmail works on low-end Chromebooks.