I'd argue that running something on a VPS is lot more a "forever service" than abusing Github's free tier for something that's not covered by their ToS.
I think the amount of time (work) you have put into this would have given you enough dollars to rent a smallish vps for longer than the life expectancy of GitHub.
$50/hour = assuming 10 hours total = $500
A droplet on DO costs $5/month. On few others, it's down to 3$/month.
That will run you about 8-10 years with yearly discounts.
Yes, you are right. Actually I have 3 vps of mine, but the workflows I want to do is so simple, just like rss -> telegram notice, and some filter, I don't intend to run a big process for this on vps. I believe some others have similar need too, so, I made this to help them save time.