I'm struggling to have APA7 references using the classic thesis style by André Miede (see here for the template I'm using).
The initial biblatex options are as follows:
\PassOptionsToPackage{%
backend = bibtex8, bibencoding = ascii,%
language = auto,%
style = numeric-comp,%
sorting = nyt, % name, year, title
maxbibnames = 10, % default: 3, et al.
natbib = true % natbib compatibility mode (\citep and \citet still work)
}{biblatex}
\usepackage{biblatex}
I modified them to have APA7 formatting:
\PassOptionsToPackage{%
% backend=biber, %instead of bibtex
backend = bibtex8, bibencoding = ascii,%
language = auto,%
style = apa,
natbib = true % natbib compatibility mode (\citep and \citet still work)
}{biblatex}
\usepackage{biblatex}
This is working, but I have this mistake:
Package biblatex Error: Biber backend is required by style.
l.16 \RequireBiber[3]
The selected style or one of the .bib files requires Biber.
It will not work at all with BibTeX..
If I'm using biber instead of bibtex8, the citations are not printed:
I would really appreciate some help here... Thanks a lot.

biberis strictly required. You can simply removebackend = bibtex8or explicitly declarebackend=biber– Ivan Jun 21 '21 at 17:29biblatex-apa.biblatex-apasimply does not work with BibTeX or BibTeX8. So you should replacebackend=bibtex8,withbackend=biber,. Usually that is not enough. You also need to make sure to call Biber instead of BibTeX/BibTeX8 when you compile your document. If you run compilation from the command line that is as easy as sayingbiber fileinstead ofbibtex file. But if you are using an editor to run the compilation steps for you, you may have to reconfigure it as shown in https://tex.stackexchange.com/q/154751/35864 – moewe Jun 21 '21 at 18:36