Having only worked in one company, a fellow colleague could argue there's a resemblance in the code design and tech stack used in my side project. I started my side project before I started this work, but after getting used to some patterns and technologies doing 9-to-5, they started getting used on side projects too. The resemblance ends there and the products are not related. Consequently, I quickly got experienced in the technologies used in my team's scope.
Is this kind of similarity, using the same "toolbox" you use at work for side projects, an issue when deciding to open source a project?
A few years ago I used to gawk at people who were rewriting boring old programs like "grep" and "cat" from
https://www.amazon.com/Software-Tools-Brian-W-Kernighan/dp/0...
in Rust but it's really appropriate because if you tried to write something interesting and innovative with difficult requirements while learning how to fight with the borrow checker.
For the past decade I've been using mainly Python and Java. Usually I am using one for paid work and the other for side projects. If you want to change the world in a big or a small way stick to languages that are commercially important.
The one trouble is that you don't want your employer to think that their IP walked out in your side project.
If they are small they wont have the money to make a case against you.
If you are brushing up your CV are you looking for a new job?
I don't think it's in your best interest to talk about that project with colleagues. Likely no one will even notice
Assuming none of the tech stack is proprietary, patented, etc. you should be fine to continue using it as you see fit. And as you mentioned you're not creating a conflict of interest so that shouldn't be an issue either.