Rather than mucking with the permissions with your home folder, which ends up with bad results as I've tried, you should just change the bitcoin user/group to whatever your own user and group are.
Then you need to change some of the entries to remove the system wide folders:
Code:
ExecStartPre=/bin/chgrp bitcoin /etc/bitcoin < ------ You don't need this
...
User=bitcoin < -------- Change to your own user
Group=bitcoin < -------- Change to your own group
### You should probably remove all this since the paths
### can't be changed to outside /run, /etc and so on
# /run/bitcoind
RuntimeDirectory=bitcoind < -------- not sure if this also needs changes or not...???
RuntimeDirectoryMode=0710 < -------- not sure if this also needs changes or not...???
# /etc/bitcoin
ConfigurationDirectory=bitcoin < -------- not sure if this also needs changes or not...???
ConfigurationDirectoryMode=0710 < -------- not sure if this also needs changes or not...???
# /var/lib/bitcoind
StateDirectory=bitcoind < -------- not sure if this also needs changes or not...???
StateDirectoryMode=0710 < -------- not sure if this also needs changes or not...???
###
# Hardening measures
####################
# Provide a private /tmp and /var/tmp.
PrivateTmp=true
# Mount /usr, /boot/ and /etc read-only for the process.
ProtectSystem=full
# Deny access to /home, /root and /run/user
ProtectHome=true < ----- I would probably remove this since your bitcoind is in /home but leave the rest as is
# Disallow the process and all of its children to gain
# new privileges through execve().
NoNewPrivileges=true
# Use a new /dev namespace only populated with API pseudo devices
# such as /dev/null, /dev/zero and /dev/random.
PrivateDevices=true
# Deny the creation of writable and executable memory mappings.
MemoryDenyWriteExecute=true
The Hardening entries are security measures to reduce damage someone with a crazy-looking ZMQ message (think blocks and transactions from other peers) can do to your node.
I know this isn't relevant to your problem, but in an ideal case if you have different bitcoin core builds, each would be in a different folder directly under your home folder, each with the stuff that would've normally been under ~/.bitcoin be in their own folder, so for instance a bitcoin.conf file under ./etc, a bitcoind.pid file under ./run, your wallets, blocks and chainstate and stuff under ./var instead of it using the system wide paths.
Basically such a topology would look like his:
home /
notatether /
bitcoin-0.21 /
etc /
bitcoin.conf
bin /
...
lib /
...
run /
bitcoind.pid
var / <-- Symlink this to your external disk using this kind of folder structure
wallets/
chainstate/
blocks/
debug.log
...
bitcoin-0.20 /
...
This allows you to have multiple systemd unit files to launch each of these different bitcoind folders.
