Raspbian is Debian based therefore we should follow the instructions for installing on Debian.
However following these instructions shows that this repo doesn't support the armhf
architecture.
N: Skipping acquire of configured file 'main/binary-armhf/Packages' as repository 'https://notesalexp.org/tesseract-ocr/stretch stretch InRelease' doesn't support architecture 'armhf'
I was able to build from the Git source and install using the following commands from these instructions:
$ git clone --depth 1 https://github.com/tesseract-ocr/tesseract.git
$ cd tesseract-ocr/
$ ./autogen.sh
$ ./configure
$ make
$ sudo make install
$ sudo ldconfig
$ tesseract -v
tesseract 4.0.0-beta.3
leptonica-1.74.1
libgif 5.1.4 : libjpeg 6b (libjpeg-turbo 1.5.1) : libpng 1.6.28 : libtiff 4.0.8 : zlib 1.2.8 : libwebp 0.5.2 : libopenjp2 2.1.2
Hey, guess what ... it works!
$ tesseract img.png outputbase
Tesseract Open Source OCR Engine v4.0.0-beta.3 with Leptonica
$ more outputbase.txt
The (quick) [brown] {fox} jumps!
Over the $43,456.78 <lazy> #90 dog
& duck/goose, as 12.5% of E-mail
from aspammer@website.com is spam.
Der ,schnelle” braune Fuchs springt
iiber den faulen Hund. Le renard brun
«rapide» saute par-dessus le chien
paresseux. La volpe marrone rapida
salta sopra il cane pigro. El zorro
marron ripido salta sobre el perro
perezoso. A raposa marrom ripida
salta sobre o cdo preguigoso.
For this image: 