We have a mix of Asus Chromeboxes 4 with 4.19 kernel and Pixelbooks with 5.4 kernel (older device but newer kernel).
I’m looking for a way to replace Cisco AnyConnect. I tried native Wireguard which is not available on 4.19 and is grayed out connect on 5.4. Since we have <5 machines who need VPN, maybe getting newer hardware for Wireguard would work.
I also tried native OpenVPN but Mikrotik router on the other end is really not good with OpenVPN, so I think there will be trouble getting this to work reliably.
What are other VPN options to connect to internal servers from outside?
Chrome OS does not have any VPN support built in, one has to rely on Android apps. I would highly recommend using strongSwan app (straight from Google Play) with IKEv2 VPN of your choice (for example strongSwan daemon on your Linux/FreeBSD server).
Not really and it shows vividly that you didn’t even read the article you’ve linked. The best you’ll get in most Chrome devices running current stable (105/106) is L2TP (no sane person would use this in 2022) and painfully poorly implemented OpenVPN. Literally nothing else without installing 3rd party software.
You are correct. I thought it would be easy enough to import an ovpn file in ChromeOS - nope! If you are unfortunate enough to be using ChromeOS Flex then your best bet is to use the CLI to connect to OpenVPN, but that is a headache. Alternatively you could try to get the in-built OpenVPN to work by messing around with certificates, assuming you are experienced with that.