With xxd version 2022-01-14 (coming with vim 8.2.4088) or newer, you can now use '-p'-p and '-c'-c with value 0 as said in the man pageman page:
-ccols |-colscolsFormat cols octets per line. Default 16 (
-i: 12,-ps: 30,-b: 6). Max 256. No maxmimum [sic]No maximum for-ps. With-ps, 0 results in one long line of output.
forFor example:
$ echo "Lorem Ipsum is simply dummy text of the printing and typesetting industry." | xxd -p -c0
4c6f72656d20497073756d2069732073696d706c792064756d6d792074657874206f6620746865207072696e74696e6720616e64207479706573657474696e6720696e6475737472792e0a