@Martin ...
"I am dependant on my webhosting provider (or their app provider Softaculous)"
in the Softac Screen for moodle in hosting provider - upper right hand corner, there is a link to Softac Support.
Provided here:
https://softaculous.deskuss.com/
"workaround to upgrade" - don't use Softac! But that means you'll have to do your homework:
1st is does your hosting lease have the required PHP versions + php extensions as well as required version of MariaDB or MySQL.
which you can do going to Server Admin Environment - update component.
You probably have a cPanel app called 'Easy Apache' - a misnomer really as it has to do with PHP version + PHP extensions to run per site/domain. So check that out also!
https://docs.cpanel.net/ea4/basics/easyapache-4-faq/
2nd: read the official Moodle docs on upgrading.
https://docs.moodle.org/401/en/Upgrading
Above is for version 4.1.
And do heed what it recommends ... make a full site backup prior to attempts to upgrading.
3rd: got any addons? Check those as well to assure they have compat version for destination version. Themes are addons ... there are 2 themes that come with Moodle code: boost is one ... and it's best, me thinks, to force the site to use boost for the duration of your march or upgrade path by adding a line to config.php:
$CFG->theme='boost';
Once you arrive at destination, your 3rd party theme should have an update available ... get it. If that update goes ok, then you can comment out the line above by adding // in front of it.
'SoS', Ken