Thanks for the ldd output.
libpcsclite.so.1 is the lib to used the pcscd socket, and is used by modules libstpkcs11.so, libeToken.so.10.7.77 and libopensc.so.8 (see below)   It is not used in libbit4xpki.so which may be a software pkcs11 or does not use pcscd.  

libcrypto.so.1.1 is OpenSSL-1.1 and also used by modules libstpkcs11.so and opensc-pkcs11.so

So libstpkcs11.so, libeToken.so.10.7.77 and libstpkcs11.so, libeToken.so.10.7.77 all appear to work as all the libs are available.

The difference is opensc-pkcs11.so needs to load libopensc.so.8 and a few others that I have not looked at 


On a 22.04.1 system running the command  `sudo snap run --shell firefox.firefox` will run snap as root to have snap start up a shell with the environment that firefox would run under. 

The `df` command shows:
 
/dev/sda3       122388080  11202960  104921928  10% /var/lib/snapd/hostfs
tmpfs              814036      1272     812764   1% /run
tmpfs                5120         4       5116   1% /run/lock
tmpfs              814036       100     813936   1% /run/user/1000
/dev/loop0            128       128          0 100% /snap/bare/5
/dev/loop1          63488     63488          0 100% /snap/core20/1587
/dev/loop2          63488     63488          0 100% /
/dev/loop3         167296    167296          0 100% /snap/firefox/1635
/dev/loop4         181248    181248          0 100% /snap/firefox/1749
/dev/loop5         410496    410496          0 100% /snap/gnome-3-38-2004/112
/dev/loop7          48128     48128          0 100% /snap/snapd/16292
/dev/loop6          93952     93952          0 100% /snap/gtk-common-themes/1535
/dev/sda2          524252      5364     518888   2% /var/lib/snapd/hostfs/boot/efi
Argonne        1952871748 479641924 1473229824  25% /media/sf_Argonne
VM-Shared      1952871748 479641924 1473229824  25% /media/sf_VM-Shared
/dev/loop8         354688    354688          0 100% /snap/gnome-3-38-2004/115
udev              4034884         0    4034884   0% /dev
tmpfs             4070180         0    4070180   0% /dev/shm
tmpfs             4070180         0    4070180   0% /snap/firefox/1749/data-dir/icons
tmpfs             4070180         0    4070180   0% /snap/firefox/1749/data-dir/sounds
tmpfs             4070180         0    4070180   0% /snap/firefox/1749/data-dir/themes
tmpfs             4070180      1996    4068184   1% /usr/lib/x86_64-linux-gnu
tmpfs             4070180         0    4070180   0% /usr/share

and /var/lib/snapd/hostfs is the host's filesystem. I was able to copy libopensc.so.8.0.0 and symlink libopensc.so.8.0.0 to /usr/lib/x86_64-linux-gnu FF will still not load opensc-pkcs11.so and it will be gone on a reboot. 

snap does set sone environemt variables that could help:
LD_PRELOAD=:/snap/firefox/1749/gnome-platform/$LIB/bindtextdomain.so
LD_LIBRARY_PATH=/var/lib/snapd/lib/gl:/var/lib/snapd/lib/gl32:/var/lib/snapd/void:/snap/firefox/1749/usr/lib:/snap/firefox/1749/usr/lib/x86_64-linux-gnu:/snap/firefox/1749/gnome-platform/lib/x86_64-linux-gnu:/snap/firefox/1749/gnome-platform/usr/lib/x86_64-linux-gnu:/snap/firefox/1749/gnome-platform/usr/lib:/snap/firefox/1749/gnome-platform/lib:/snap/firefox/1749/gnome-platform/usr/lib/x86_64-linux-gnu/dri:/var/lib/snapd/lib/gl:/snap/firefox/1749/gnome-platform/usr/lib/x86_64-linux-gnu/libunity:/snap/firefox/1749/gnome-platform/usr/lib/x86_64-linux-gnu/pulseaudio


So this is where I am at. Firefox-esr from debiaen works with opensc. Forefox from snap does not. It appears the some effort when it to geting p11-kit to start, but all p11-kit does is load other pkcs11 modules, that may have been installed using normal apt-get. It the initial comments of this bug report there were suggestions to copy the single file if a pkcs11 module to a "doc" directory, but no attempt was made to copy dependent libraries that the module needs. 

These will only work if missing libraries are in the snap base or of firefox snap packages.   

OpenSC also has a notify capability to tell the user when a card was inserted or removed. This may add additional complications to getting it to work under snap.   

Not much else I can do.