Applying Fix Pack 3 to HCL Notes 14 resolved the issue. The connection can be established with TLSv1.3 as expected. The JVM was also updated with the Fix Pack to IBM Semeru Runtime Open Edition 17.0.12.1 (build 17.0.12+7). I don't know if the updated JVM or something other within HCL Notes 14 was the root cause of the issue.