I need to type both English and Hebrew in the same document.
I don’t want all the menus to change to Hebrew (which I don’t really understand). My version is Linux and 7.3.
FWIW, changing the (virtual) keyboard layout (to Hebrew in this case) should allow to type-in characters in Write in that language.
The UI language does not have to change. You could type-in characters in Hebrew, English, Spanish and Chinese, all in the same document, while the UI is still using English as language setting (for menus, keyboard shortcuts, etc.).
Since English and Hebrew use different language scripts, LO Write will recognize each word automatically, so even spell-checking should work. This is true even without using Styles.
What is needed is for you to set the needed languages appropriately in Write menu Tools > Options > Languages and Locales (in version 24.2+).
Additionally (or rather, beforehand), you need to add the Hebrew language/script as alternative/available in your OS settings (so at least a virtual keyboard layout can be used in order to type-in characters in that language alphabet/script). Your OS will still use your original language, of course. For example, if you only have the English (USA) keyboard layout, you probably need to add a (virtual) Hebrew keyboard layout in order to type-in characters in Hebrew. I guess that the alternative would be to use the Insert Special Character menu in Write, but that sounds inefficient unless you just need a couple of characters.
UI language and document language(s) are two different independent things.
What you want is a multi-lingual document. This is a complex task if you don’t master the style concept. With correctly crafted styles, you tell Writer which language is used in the pieces of the document. This instructs the spelling checker as to which dictionary to use.
Typing is another issue. You didn’t tell which routine you follow keyboard-wise. I type only documents needing the Latin alphabet. And since I am not a touch typist, I don’t switch my keyboard layout. I customised it so that all my needed most frequent characters are available with Alt Gr, Shift and combination.
With languages as different as Hebrew and English, you are probably accustomed to layout switch. Unfortunately, under Linux this keyboard switch is not forwarded to LO (nor to any application as far as I know, though there seems to be some encouraging results with GTK+, i.e. Gnome and similar desktops; unfortunately none with Qt, i.e. KDE Plasma et al.). Therefore, you need to manually apply a style if you want to correctly spellcheck your text.
Don’t forget to enable the ad hoc document language in Tools
>Options
, Language Settings
>Languages
(wording changed in 24.x) so that extra options in dialogs and menus are activated. In particular, this allows you to select different fonts/sizes/… for English and Hebrew.