Nope, its not solved, shit is still there lol. For example webrtc will leak oryginal IP (and thats just one example, there are more). You can block webrtc, original IP wont be leaked but most real users dont even know what webrtc is so blocking webrtc can make whole activity suspicious.
best thing @OP can do:
On 1 pc in your office install proxmox and configure it, make as many VMs as you need (without clonning VMs). Install windows or ubuntu desktop, both will be fine.
Connect this PC to LTE router
Login to tumblr acc 1 from vm 1, reboot router, login to acc2 reboot router etc.
Dont forget to reboot router when switching accounts.
P.S.
Before doing all above visit whatsmyip.org or similar site and check few times what IP you get after reboot to be sure you get fresh IP after each reboot.