When using my low profile filament spool stand i had the problem to guide the filament the usual way into my Prusa MK3s. To enable this i designed this ring, which can be placed on the usual filament holder.

First screw two PTFE tube quick connectors with a 6mm thread into the two holes of the prolounging part. Now put a small 30cm PTFE tube into the front quick connector which os pointing towards your print head.
Based on the position of your externally placed filament spool you can use any length of PTFE tube to guide the filament all the way to your printer and stick this tube into the backside quick connector.
For the external side I am using 1,5m of PTFE tube with no issues. More than 3 kg of filament has beed fed through my assembly with no signs of any visual wear.

To reduce noise, movement and possibly wear while printing through this assembly, I am using velcro strips to fix it to the filament holder.

The model can be printed on the side with no support material needed.