Sure. My NAS I use for backups is also made from ancient desktop PC running ownCloud. The system is slow-ish by today's standards, but since I had it already, I could invest in bigger SSD for data storage.
Unless you consider fighting adblockers a futile stupidity, you should first apply Occam's razor - explanation requiring least amount of assumptions is probably the correct one.
In this case spoofing user-agent string of Chrome is enough to fix all the performance issues on Firefox, meaning there is no fancy anti-adblock code or anything like that.
Wtf, I thought this was a meme...