Viele Dank euch Beiden. Ich konnte jetzt erfolgreich die aktuelle libvips-version bauen.
Jetzt funktioniert alles. 
Ich habe es wie folgt gemacht:
cd /tmp
wget https://github.com/libvips/libvips/releases/download/v8.9.2/vips-8.9.2.tar.gz
tar xf vips-8.9.2.tar.gz
cd vips-8.9.2
./configure
make
sudo make install
sudo ldconfig
Danach Sharp installiert.
cd /opt/iobroker
npm i sharp
Ohne Errors - Log:
rock64@rock64:/opt/iobroker$ npm i sharp
> sharp@0.25.2 install /opt/iobroker/node_modules/sharp
> (node install/libvips && node install/dll-copy && prebuild-install --runtime=napi) || (node-gyp rebuild && node install/dll-copy)
info sharp Detected globally-installed libvips v8.9.2
info sharp Building from source via node-gyp
make: Entering directory '/opt/iobroker/node_modules/sharp/build'
CC(target) Release/obj.target/nothing/../node-addon-api/src/nothing.o
AR(target) Release/obj.target/../node-addon-api/src/nothing.a
COPY Release/nothing.a
TOUCH Release/obj.target/libvips-cpp.stamp
CXX(target) Release/obj.target/sharp/src/common.o
CXX(target) Release/obj.target/sharp/src/metadata.o
CXX(target) Release/obj.target/sharp/src/stats.o
CXX(target) Release/obj.target/sharp/src/operations.o
CXX(target) Release/obj.target/sharp/src/pipeline.o
CXX(target) Release/obj.target/sharp/src/utilities.o
CXX(target) Release/obj.target/sharp/src/sharp.o
SOLINK_MODULE(target) Release/obj.target/sharp.node
COPY Release/sharp.node
make: Leaving directory '/opt/iobroker/node_modules/sharp/build'
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@2.1.3 (node_modules/fsevents):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.1.3: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"arm64"})
npm WARN optional SKIPPING OPTIONAL DEPENDENCY: osx-temperature-sensor@1.0.5 (node_modules/osx-temperature-sensor):
npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for osx-temperature-sensor@1.0.5: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"arm64"})
+ sharp@0.25.2
added 4 packages from 112 contributors in 137.029s
22 packages are looking for funding
run `npm fund` for details
rock64@rock64:/opt/iobroker$
Zur Sicherheit nochmal den "Fixer" ausgeführt. Wahrscheinlich nicht notwendig, aber schadet ja auch nicht
iobroker stop
iobroker fix
iobroker start
Grüße
Nachdem der "Fensterstatus" aktualisiert wurde, funktioniert auch alles ...
