Not sure if it is after the update, but any operation at web-ui, including each login step, just takes 120+ seconds. Even any operation: going to any page takes 120-150 and maybe more time. I had to remove 2FA from CLI to even be able to login. Now, each step is like a big pain. 
I can’t reproduce this issue on any of my servers.
Did you check the log /var/log/hestia/nginx-error.log? Disk space? Load?
I had checked literally every log. Nothing helped. Then I started digging with the help of a friend, and it turns out something related to eth1/2/3/4/5/6/7/8/9 were present in the network. I have reached out to Netcup as well, to see what they have to say for themselves. Seems
running ifdown --force eth0 did solve it.
ls -la /run/network/
total 20
drwxr-xr-x 2 root root 180 Jul 19 18:11 .
drwxr-xr-x 29 root root 880 Jul 19 17:57 ..
-rw-r--r-- 1 root root 6 Jul 19 18:11 ifstate
-rw-r--r-- 1 root root 1 Jul 19 18:11 ifstate.eth0
-rw-r--r-- 1 root root 1 Jul 19 18:09 ifstate.eth1
-rw-r--r-- 1 root root 1 Jul 19 18:09 ifstate.eth2
-rw-r--r-- 1 root root 3 Jul 19 16:40 ifstate.lo
-rw-r--r-- 1 root root 0 Jul 19 16:40 .ifstate.lock
-rw-r--r-- 1 root root 0 Jul 19 18:11 restart-hotplug
drwxr-xr-x 2 root root 140 Jul 19 18:19 .
drwxr-xr-x 29 root root 880 Jul 19 18:20 ..
-rw-r--r-- 1 root root 6 Jul 19 18:19 ifstate
-rw-r--r-- 1 root root 1 Jul 19 18:19 ifstate.eth0
-rw-r--r-- 1 root root 3 Jul 19 18:19 ifstate.lo
-rw-r--r-- 1 root root 0 Jul 19 18:19 .ifstate.lock
-rw-r--r-- 1 root root 0 Jul 19 18:19 restart-hotplug
Deleted these unwanted entries, rebooted server from their control panel, and now checking 2FA again.
Also ran sudo systemctl reset-failed networking.service
Added 2FA, rebooted, and it works now.
Just for more context, these entries were also there in /etc/sysctl.d/50-IPv6.conf, wherein I removed all eth1/2/3/4/5/6/7/8/9 entries.
net.ipv6.conf.default.accept_ra=0
net.ipv6.conf.default.autoconf=0
net.ipv6.conf.all.accept_ra=0
net.ipv6.conf.all.autoconf=0
net.ipv6.conf.eth0.accept_ra=0
net.ipv6.conf.eth0.autoconf=0
net.ipv6.conf.eth1.accept_ra=0
net.ipv6.conf.eth1.autoconf=0
net.ipv6.conf.eth2.accept_ra=0
net.ipv6.conf.eth2.autoconf=0
net.ipv6.conf.eth3.accept_ra=0
net.ipv6.conf.eth3.autoconf=0
net.ipv6.conf.eth4.accept_ra=0
net.ipv6.conf.eth4.autoconf=0
net.ipv6.conf.eth5.accept_ra=0
net.ipv6.conf.eth5.autoconf=0
net.ipv6.conf.eth6.accept_ra=0
net.ipv6.conf.eth6.autoconf=0
net.ipv6.conf.eth7.accept_ra=0
net.ipv6.conf.eth7.autoconf=0
net.ipv6.conf.eth8.accept_ra=0
net.ipv6.conf.eth8.autoconf=0
net.ipv6.conf.eth9.accept_ra=0
net.ipv6.conf.eth9.autoconf=0
@sahsanu This issue seems to be due to the server provider, right?
At least network issues for sure, so not really related to hestia.