If you have running LXC container on your router, I suggest doing backup. It should work to bring the existing once from Turris OS 3.x to Turris OS 4.x, but I didn’t try it as I am not using LXC on Turris 1.1 router anymore. I had it for Tvheadend, but I compiled it for OpenWrt.
Otherwise, to setup a new one can be problematic as powerpcspe were removed from Debian ports.
Thread in Czech section:
Anyway for more details why it was removed you can read e-mail from Debian maintainer of powerpcpse Re: Removing powerpcspe from Debian Ports
Here is kernel configuration on Turris 1.1, which is running Turris OS 4.0.3.
root@turris:~# zcat /proc/config.gz | grep CGROUP
CONFIG_CGROUPS=y
CONFIG_BLK_CGROUP=y
# CONFIG_DEBUG_BLK_CGROUP is not set
CONFIG_CGROUP_WRITEBACK=y
CONFIG_CGROUP_SCHED=y
CONFIG_CGROUP_PIDS=y
# CONFIG_CGROUP_RDMA is not set
CONFIG_CGROUP_FREEZER=y
CONFIG_CGROUP_DEVICE=y
CONFIG_CGROUP_CPUACCT=y
# CONFIG_CGROUP_BPF is not set
CONFIG_CGROUP_DEBUG=y
CONFIG_SOCK_CGROUP_DATA=y
# CONFIG_NETFILTER_XT_MATCH_CGROUP is not set
CONFIG_NET_CLS_CGROUP=y
# CONFIG_CGROUP_NET_PRIO is not set
CONFIG_CGROUP_NET_CLASSID=yMore options will be enabled in Turris OS 5.x according to this pull request, which I have on review. Once it is merged, it should be quite easier to have/run Docker on Turris Omnia, Turris MOX.
Not sure, if they will be backported in Turris OS 4.x. Most likely I doubt.
Package shellinabox wasn’t and still isn’t part of Turris OS / OpenWrt. If you would like to have it in OpenWrt, you will need to send a pull request to packages repository. In the morning, I take a look, why you couldn’t compile it. You are right that it is related to a new version of OpenSSL, but there is a year pending pull request, which was not accepted nor reviewed by developers of shellinabox and the guy who sent the PR is taking care of OpenSSL in OpenWrt. So, you just need to download it as a patch and put it to patch folder inside shellinabox.
About CUPS, it is complicated. More answers later…