My solution while not perfect, does work is to put one of my Raspberry
Pi 5's to work, running "PrusaSlicer"... I'll do the grumpy old guy
thing of noting I'm not super keen on the differences between "Slic3r"
and "PrusaSlicer", but ... better a working but flawed (or at least
different) ... software tool than no software tool.
Slic3r is dead. Last updated in 2018. PrusaSlicer is the fork and continuing the work. There are now a few forks of PrusaSlicer, such as SuperSlicer and OrcaSlicer.
I didn't like Slic3r when I started printing, and I used Cura (
https://curaslicer.com/). Later I bought a Prusa printer and so I use PrusaSlicer now.
You didn't say what printer you have and since you are using old software, I hope you have updated your printer firmware. Many printers before 2018 did not have thermal runaway detection and other safety features back then and many printers had high risk of catching fire.
Andrew