Welcome to the forums! Most of the members here only run GNU/Linux so are not likely to run MS applications, so chances are realistically low that someone here has experience with converting a MS-Access Application to another format.
To follow on from
@f33dm3bits - Despite the huge number of users registered here, there is only a small, active community of regular contributors. All spread out, in different timezones around the world.
Most are ordinary, non-technical desktop users - and many of us completely abandoned Windows a long time ago.
There are very few professional Linux sys-admins and programmers in the community.
I'm one of the few professional programmers. I've had a lot of experience porting programs from one programming/scripting language to another. And at a previous job (over 15 years ago) - I did a lot of enterprise level database programming. But haven't used MS access since I was a teenager at school (30 odd years ago) and haven't yet used Libreoffice's database offering - so unfortunately - I can't give any specific advice because I have no direct experience with these pieces of software. I use pretty much everything else in Libreoffice, but I haven't used its database, or its VB-like macro language.
If you are interested in this Dutch accounting application, do this (in Windows)
1, Create the folder Boeket
2. Download
https://app.box.com/s/nwtg0a4he3z6zd7evzyv5g8pi3rcbldj
3. Install it unpacked in the folder Boeket
4. Start with boeket.accdb
Regarding the above - I've just downloaded the application. I'll take a look at it in access on my Windows work PC during my lunch-break and will try to take a look at the VB under the hood.
As all of the VB is contained in the Access database - porting to Libreoffice will probably be the simplest option. However - because it's the simplest option, doesn't mean it won't still be difficult, or painless...
I'll try opening it in the Windows version of Libreoffice on my work PC and will see if it runs at all and see if there are any problematic bits of VB that will need to be altered/rewritten.
NOTE: ** I abandoned Windows a long time ago on my own PCs, but my current employers use Windows **
Then it's a case of looking at Libreoffice's documentation for their Basic language and try to find equivalent functionality for the problematic areas.
Libreoffice has some documention regarding running VBA macros in MS office documents here:
help.libreoffice.org
And there is extensive documentation on Libreoffice's basic language here:
help.libreoffice.org
If I run out of time on my lunch-break, then I'll take a look at it in Libreoffice on my Linux laptop tonight and will get back to you with my findings once I've finished investigating.
It might be a trivial job to get it running in libre-office, or it might be a much more involved process.
In the worst case scenario - It may require a complete re-write, from the ground up using a different database and a different programming language.
But again, if it comes to a complete re-write from the ground up - which programming language and database would you choose? Because there are a LOT of possibilities!
In the meantime - you might also want to consider looking for help in libreoffice's user community:
<a href="https://ask.libreoffice.org/t/this-is-the-guide-how-to-use-the-ask-site/10">This</a> is intended to help you use this website.<br> There will be additions to this website as we go along.<br> Bring a positive spirit to your posts, and thank you.
ask.libreoffice.org
Some other places to seek help/advice are listed here:
community support, community, support, LibreOffice, mailing lists, help, forum, IRC, questions, bugs
www.libreoffice.org