I had posted before about mobile issues and virtualmin/webmin before. I thought I had the answer by re-installing from scratch, but that didn't pan out either. So, spec's first:
Webmin 1.9 Usermin 1.751 Virtualmin 6.06 CSF 12.10 Kernel & CPU Linux 3.10.0-957.12.1.el7.x86_64 on x86_64 CentOS Linux 7.6.1810
All software is up to date.
Issue: I can connect to virtualmin via home network (wired and wireless). I can connect to the websites just the same. On my Boost Mobile (don't know if it's specific or not, so why not specify right?) running Android 7.1.2 and backup running 8.1.0, I can connect to the websites just fine, however, connection to virtualmin/webmin timesout.
I have the wbt-virtual-server-mobile-theme installed. There's nothing in the /var/logs that I can find regarding this and the ip address for the phones is in the permitted list of CSF. However, I'm thinking it's more specific to the mobile network.
I have used the mobile hotspot feature of both my primary and backup phone to connect to the net via wireless. It too failed and timed out on attempting to connect to the webmin/virtualmin, but not the websites.
This does affect the ability for the phones to receive and send emails.
Hmm, there's nothing within Virtualmin that should cause problems with mobile devices, and that's how a lot of people need to access it these days.
If you're finding that you are unable to access Webmin/Virtualmin on port 10000, that could indicate that your provider may be blocking some ports for some reason.
It could also be some sort of firewall on your Android device itself, though I don't believe I've run into that before.
However, just to rule out an issue on the server, you could always try disabling CSF, as it's possible it's blocking it for some reason.
If its timing out then CSF is blocking it or upstream DNS hasnt updated yet on the cell network. Did you check the csf.deny file to be sure your cell IPs are not in there? Maybe from previous wrong passwords on tiny phone keyboard. First, I'd turn off CSF and test again just to see if it is firewall. If successful, IP must be in csf.deny file. Which is located /etc/csf/csf.deny
Using the phone's "About->Status" to check the IP address against CSF deny (and using the search in CSF), it isn't listed there. I checked both IPv4 and v6.