bundle exec jekyll serve execution fails

[roarinpenguin]

On a kali 2021.2 running Ruby 2.7, the command
bundle exec jekyll serve
fails with the following error:
"/home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/tags/include.rb:194: warning: Using the last argument as keyword parameters is deprecated
Liquid Exception: Liquid syntax error (line 8): Unknown tag 'when' in vendor/bundle/ruby/2.7.0/gems/liquid-4.0.3/lib/liquid/locales/en.yml
jekyll 3.8.5 | Error: Liquid syntax error (line 8): Unknown tag 'when'
Traceback (most recent call last):
33: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/bin/jekyll:25:in <main>' 32: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/bin/jekyll:25:in load'
31: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/exe/jekyll:15:in <top (required)>' 30: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/mercenary-0.3.6/lib/mercenary.rb:19:in program'
29: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/mercenary-0.3.6/lib/mercenary/program.rb:42:in go' 28: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in execute'
27: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in each' 26: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in block in execute'
25: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/commands/serve.rb:75:in block (2 levels) in init_with_program' 24: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/commands/serve.rb:93:in start'
23: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/commands/serve.rb:93:in each' 22: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/commands/serve.rb:93:in block in start'
21: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/commands/build.rb:36:in process' 20: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/commands/build.rb:65:in build'
19: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/command.rb:28:in process_site' 18: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:71:in process'
17: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:192:in render' 16: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:471:in render_pages'
15: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:471:in each' 14: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:472:in block in render_pages'
13: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/site.rb:479:in render_regenerated' 12: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/renderer.rb:62:in run'
11: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/renderer.rb:79:in render_document' 10: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/renderer.rb:121:in render_liquid'
9: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/liquid_renderer/file.rb:12:in parse' 8: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/liquid_renderer/file.rb:49:in measure_time'
7: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/jekyll-3.8.5/lib/jekyll/liquid_renderer/file.rb:13:in block in parse' 6: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/liquid-4.0.3/lib/liquid/template.rb:116:in parse'
5: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/liquid-4.0.3/lib/liquid/template.rb:132:in parse' 4: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/liquid-4.0.3/lib/liquid/document.rb:5:in parse'
3: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/liquid-4.0.3/lib/liquid/document.rb:10:in parse' 2: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/liquid-4.0.3/lib/liquid/block_body.rb:32:in parse'
1: from /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/liquid-4.0.3/lib/liquid/document.rb:11:in block in parse' /home/kali/Desktop/mitrecnd.github.io/vendor/bundle/ruby/2.7.0/gems/liquid-4.0.3/lib/liquid/document.rb:23:in unknown_tag': Liquid syntax error (line 8): Unknown tag 'when' (Liquid::SyntaxError)
"

Please advise, thanks.