Honestly, for your use case, you should just get a older cell phone. Put lineage OS on it, or calyxos.. share your VPN over hotspot, these are the only two ROMs that I'm aware of that allow you to do that. This has the benefit that the VPN traffic looks just like for traffic from the phone, and you don't have to do any gymnastics to modify the TTL, or the operating system signature of the traffic.
Boom, travel router. Very portable, has a built-in battery etc etc etc etc etc
I like GLI-net, they are great, they have great hardware. If you want to buy it I endorse it. If you're paranoid flash your own firmware. If you use an end-to-end VPN from your device it doesn't matter what your mobile router uses. However the killer feature here, I think is better supplied by an older phone running the ROMs I mentioned above. It's just more portable. And you have a backup phone when you're traveling