PHP 8 Deprecated code, warnings and fatal errors

I have just moved a multisite to new infrastructure with PHP 8.0, and find SB Child List causes a WSD Fatal error:

[18-Feb-2022 14:35:07 UTC] PHP Warning:  Undefined array key "title" in /plugins/sb-child-list/sb_child_list.php on line 950
[18-Feb-2022 14:35:07 UTC] PHP Warning:  Undefined array key "show_parent_link" in /plugins/sb-child-list/sb_child_list.php on line 951
[18-Feb-2022 14:35:07 UTC] PHP Warning:  Undefined array key "text" in /plugins/sb-child-list/sb_child_list.php on line 952
[18-Feb-2022 14:35:07 UTC] PHP Warning:  Undefined array key "template_id" in /plugins/sb-child-list/sb_child_list.php on line 977
[18-Feb-2022 14:35:07 UTC] PHP Warning:  Undefined array key "template_id" in /plugins/sb-child-list/sb_child_list.php on line 977
[18-Feb-2022 14:35:07 UTC] PHP Warning:  Undefined array key "template_id" in /plugins/sb-child-list/sb_child_list.php on line 977
[18-Feb-2022 14:35:08 UTC] PHP Fatal error:  Uncaught TypeError: Cannot access offset of type string on string in /plugins/sb-child-list/sb_child_list.php:461
Stack trace:
#0 /wp-includes/shortcodes.php(356): sb_cl_filter_post()
#1 [internal function]: do_shortcode_tag()
#2 /wp-includes/shortcodes.php(228): preg_replace_callback()
#3 /wp-includes/class-wp-hook.php(307): do_shortcode()
#4 /wp-includes/plugin.php(189): WP_Hook->apply_filters()
#5 /wp-includes/post-template.php(253): apply_filters()
#6 /themes/genesis/lib/structure/post.php(486): the_content()
#7 /wp-includes/class-wp-hook.php(307): genesis_do_post_content()
#8 /wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters()
#9 /wp-includes/plugin.php(474): WP_Hook->do_action()
#10 /themes/genesis/lib/structure/loops.php(119): do_action()
#11 /themes/genesis/lib/structure/loops.php(38): genesis_standard_loop()
#12 /wp-includes/class-wp-hook.php(307): genesis_do_loop()
#13 /wp-includes/class-wp-hook.php(331): WP_Hook->apply_filters()
#14 /wp-includes/plugin.php(474): WP_Hook->do_action()
#15 /themes/genesis/lib/framework.php(66): do_action()
#16 /themes/genesis/page.php(15): genesis()
#17 /wp-includes/template-loader.php(106): include('...')
#18 /wp-blog-header.php(19): require_once('...')
#19 /pvirtualmin/blog/releases/20220218-084628/web/index.php(6): require('...')
#20 {main}
  thrown in /plugins/sb-child-list/sb_child_list.php on line 461