I have previously used https://f-droid.org/en/packages/org.primftpd/ to enable sftp to my android phone

For more information on How to mount remote storage using sshfs, see hpr1944 :: sshfs - Secure SHell FileSystem

Also you will need to know about some useful tools for working with Android Devices hpr3515 :: ADB and scrcpy

I found https://www.galexander.org/software/simplesshd/

SimpleSSHD is an SSH2 server based on dropbear that supports scp, sftp, and rsync. It only supports public-key based authentication (no password/interactive auth except for bootstrapping). It does not use root, which means it must listen on a port over 1024 (defaults to port 2222).

Install from fdroid

https://f-droid.org/en/packages/org.galexander.sshd

before

laptop$ adb shell

phone: # cd /data/user/0/org.galexander.sshd/files

phone:/data/user/0/org.galexander.sshd/files # ls -al

total 56

drwxrwx--x 2 u0_a268 u0_a268 4096 2022-06-17 12:06 .

drwx------ 6 u0_a268 u0_a268 4096 2022-06-17 11:59 ..

-rw-rw-rw- 1 root root 490 2022-06-17 12:05 authorized_keys

-rw------- 1 u0_a268 u0_a268 475 2022-06-17 12:07 dropbear.err

-rw------- 1 u0_a268 u0_a268 650 2022-06-17 12:03 dropbear.err.old

-rw------- 1 u0_a268 u0_a268 6 2022-06-17 12:06 dropbear.pid

-rw------- 1 u0_a268 u0_a268 83 2022-06-17 12:03 dropbear_ed25519_host_key

Commands to run

phone:/data/user/0/org.galexander.sshd/files # restorecon -F authorized_keys

SELinux: Loaded file_contexts

phone:/data/user/0/org.galexander.sshd/files # chmod 600 authorized_keys

phone:/data/user/0/org.galexander.sshd/files # chown u0_a268:u0_a268 authorized_keys

after

phone:/data/user/0/org.galexander.sshd/files # ls -al

total 56

drwxrwx--x 2 u0_a268 u0_a268 4096 2022-06-17 12:06 .

drwx------ 6 u0_a268 u0_a268 4096 2022-06-17 11:59 ..

-rw------- 1 u0_a268 u0_a268 490 2022-06-17 12:05 authorized_keys

-rw------- 1 u0_a268 u0_a268 475 2022-06-17 12:07 dropbear.err

-rw------- 1 u0_a268 u0_a268 650 2022-06-17 12:03 dropbear.err.old

-rw------- 1 u0_a268 u0_a268 6 2022-06-17 12:06 dropbear.pid

-rw------- 1 u0_a268 u0_a268 83 2022-06-17 12:03 dropbear_ed25519_host_key

laptop$ sshfs -p 2222 192.168.1.123: /mnt/phone/