After printing an even longer spoolholder (https://www.thingiverse.com/thing:4724930), I suddenly realised: Why was it getting even longer and longer??? I could just flip the spool around! And here is the result. This version is even smaller than the original side mount and is also capable of holding spools as wide as you would like (given you have the right spoolholder.) Still compatible with chains.

Creality

Ender 3 Pro

No

Yes

Printed the guides in PETG as they had to handle lots of rubbing filament, else the spool holder is made out of PLA. Filament Guides require support, spoolholder mount doesn't.