howto russian without 4 warnings per russian text

Question

\documentclass[a4paper, twoside, ngerman]{book}
\usepackage[bidi=default]{babel}

\babelprovide[main, import=de]{ngerman}
\babelprovide[import]{russian}
\babelfont[russian]{rm}{Noto Sans}

\begin{document}
    deutsch \foreignlanguage{russian}{Видео урок по живописи маслом} deutsch
\end{document} 

Throws warnings without end and advices to define a language. I did try to understand the doc but didn't get it without changing the main language font as well (Noto font looks to heavy to me and standard LaTeX font seems to have no cyrilic)...

Command Line:   xelatex.exe --interaction=errorstopmode --synctex=-1 "mwe.tex"
Startup Folder: C:\daten\Literatur\Arbeitstechniken\LaTeX\mwe

This is XeTeX, Version 3.14159265-2.6-0.999991 (TeX Live 2019/W32TeX) (preloaded format=xelatex)
 restricted \write18 enabled.
entering extended mode
(./mwe.tex
LaTeX2e <2018-12-01>
(c:/texlive/2019/texmf-dist/tex/latex/base/book.cls
Document Class: book 2018/09/03 v1.4i Standard LaTeX document class
(c:/texlive/2019/texmf-dist/tex/latex/base/bk10.clo))
(c:/texlive/2019/texmf-dist/tex/generic/babel/babel.sty
(c:/texlive/2019/texmf-dist/tex/generic/babel/switch.def)
(c:/texlive/2019/texmf-dist/tex/generic/babel-german/ngerman.ldf
(c:/texlive/2019/texmf-dist/tex/generic/babel-german/ngermanb.ldf
(c:/texlive/2019/texmf-dist/tex/generic/babel/babel.def
(c:/texlive/2019/texmf-dist/tex/generic/babel/xebabel.def
(c:/texlive/2019/texmf-dist/tex/generic/babel/txtbabel.def))))))
(c:/texlive/2019/texmf-dist/tex/generic/babel/locale/ru/babel-russian.tex)
(c:/texlive/2019/texmf-dist/tex/latex/fontspec/fontspec.sty
(c:/texlive/2019/texmf-dist/tex/latex/l3packages/xparse/xparse.sty
(c:/texlive/2019/texmf-dist/tex/latex/l3kernel/expl3.sty
(c:/texlive/2019/texmf-dist/tex/latex/l3kernel/expl3-code.tex)
(c:/texlive/2019/texmf-dist/tex/latex/l3backend/l3backend-xdvipdfmx.def)))
(c:/texlive/2019/texmf-dist/tex/latex/fontspec/fontspec-xetex.sty
(c:/texlive/2019/texmf-dist/tex/latex/base/fontenc.sty
(c:/texlive/2019/texmf-dist/tex/latex/base/tuenc.def))
(c:/texlive/2019/texmf-dist/tex/latex/fontspec/fontspec.cfg))) (./mwe.aux

Package babel Warning: The current font is not a standard family:
(babel)                "[lmroman10-regular]:mapping=tex-text;" at 10.0pt
(babel)                Script and Language are not applied. Consider
(babel)                defining a new family with \babelfont.
(babel)                Reported on input line 3.

)

Package babel Warning: The current font is not a standard family:
(babel)                "[lmroman10-regular]:mapping=tex-text;" at 10.0pt
(babel)                Script and Language are not applied. Consider
(babel)                defining a new family with \babelfont.
(babel)                Reported on input line 8.


Package fontspec Warning: Language 'Russian' not available for font 'Noto
(fontspec)                Sans' with script 'Cyrillic'.

[1] (./mwe.aux

Package babel Warning: The current font is not a standard family:
(babel)                "[lmroman10-regular]:mapping=tex-text;" at 10.0pt
(babel)                Script and Language are not applied. Consider
(babel)                defining a new family with \babelfont.
(babel)                Reported on input line 3.

) )
Output written on mwe.pdf (1 page).
SyncTeX written on mwe.synctex.

Transcript written on mwe.log.


_____________________________________________________________________

 XeLaTeX Compilation Report (Pages: 1)

 Errors: 0   Warnings: 4   Bad Boxes: 0
_____________________________________________________________________

Answer 1

You could try the Computer Modern Unicode font family:

\documentclass[a4paper]{book}

\usepackage{fontspec}
  \setromanfont{CMU Serif}
  \setsansfont{CMU Sans Serif}
  \setmonofont{CMU Typewriter Text}


\usepackage{babel}
  \babelprovide[main, import=de]{ngerman}
  \babelprovide[import]{russian}

\begin{document}
    deutsch \foreignlanguage{russian}{Видео урок по живописи маслом} deutsch
\end{document}

(If you are using xelatex you might need to install the fonts on your system)