Re #2328 Setting LXML version to any version without the known modern-CPU-only CPU flags

requirements.txt

@@ -52,7 +52,10 @@ cryptography~=3.4
 beautifulsoup4
 
 # XPath filtering, lxml is required by bs4 anyway, but put it here to be safe.
-lxml >=4.8.0,<6
+# #2328 - 5.2.0 and 5.2.1 had extra CPU flag CFLAGS set which was not compatible on older hardware
+#         It could be advantageous to run its own pypi package here with those performance flags set
+#         https://bugs.launchpad.net/lxml/+bug/2059910/comments/16
+lxml >=4.8.0,<6,!=5.2.0,!=5.2.1
 
 # XPath 2.0-3.1 support - 4.2.0 broke something?
 elementpath==4.1.5