# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/('[^']*'|[^',]*),\s*/\1\t/g;t' <<< "21, 2, '23.5R25 ETADT', 'description, with a comma'
22, 1, '26.5R25 ETADT', 'Description without a comma'
23, 5, '20.5R20.5', 'Another description with ; semicolumn'"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html