In commit 7a4fbb55 (MDEV-25105)
the innochecksum option --write (-w) was removed altogether.
It should have been made a Boolean option, so that old data files
may be converted to a format that is compatible with
innodb_checksum_algorithm=strict_crc32 by executing the following:

innochecksum -n -w ibdata* */*.ibd

It would be better to use an older-version innochecksum
for such a conversion, so that page checksums will be validated
before updating the checksum.

It never was possible for innochecksum to convert files to the
innodb_checksum_algorithm=full_crc32 format that is the default
for new InnoDB data files.