By default it is set to "Direct input" (alphanumeric characters only) for normal mode commands.
Switch to the normal input by the following method.
-  "🔤" button (function bar)
 -  One-line text box
 -  
<C-^>
 -  Vim script
 -  IME shortcuts
 
■ One-line text box
When you start one-line text box (double tap at the bottom of the screen), you can use the usual input equivalent to a normal Android application.
It is convenient to change "Preferences" -> "🔤 button" to "One-line text box".
■ Vim Script(control via Vim)
If you want to switch to the normal input automatically when enter the insert mode, add the following settings to your .vimrc.
let g:imctrl_normal=56
let g:imctrl_insert=50
let g:imctrl_normal=53
let g:imctrl_insert=50
You can also use 
<C-^>. (
:h iminsert :h i_CTRL-^)
■ Non-English language with Gboard
If you want to input non-English language characters using 
Gboard, try using the following settings.
-  Set Gboard's "Language" to only two, English and the language you want to use.
 -  Long press space key → Choose "English".
 -  Set DroidVim's "Preferences" → "functionbar" → "🔤" button to "<C-^>"
 -  Add the following settings to .vimrc and restart.
 
"Language Switch"
let g:imactivate_language_switch = 61
After that, use "🔤" button in insert mode to switch between alphanumeric characters and non-English language characters.
※ This method is not useful if you need more than two languages.
If a physical keyboard is connected, use 
<C-^> or 
<C-6>. You can also use "IME shortcuts".
-  DroidVim's "Preferences" → "Text Input Mode" → Set "IME Shortcut Action" to "<C-^>"
 
※ Unless there is a problem, do not use "[Shift] + [Space]".
■ Option details
|  imctrl_insert               |  When entering the insert mode  | 
|  imctrl_normal               |  When exiting the insert mode  | 
|  imactivate_insert           |  When entering the insert mode (iminsert=2) | 
|  imactivate_normal           |  When exiting the insert mode (iminsert=2) | 
|  imactivate_language_switch  |  When entering/exiting the insert mode (iminsert=2) | 
The operation differs depending on the IME being used. Please set appropriately by referring to “Setting value details” in the next section.
■ Setting value details
You can change the text input mode from Vim script.
:ATEMod 72
|  0 |  Do nothing  |  | 
| 50 |  Normal input |  | 
| 51 |  Direct input : password  |  | 
| 52 |  Direct input : URI  |  | 
| 53 |  Direct input : Default  |  | 
| 54 |  Direct input : Raw  |  | 
| 55 |  Toggle "Normal input"/"Input mode at startup" |  See Preferences  | 
| 56 |  One-line text box  |  | 
| 61 |  Language switch (Shift+Space)  |  If you are using IME for which "language switch" command is not enabled, the same process as pressing the space key is performed.  | 
| 62 |  Language switch (Alt+Space)  |   If you are using IME for which "language switch" command is not enabled, the same process as pressing the space key is performed.  | 
| 63 |  <C-^>  |  For iminsert  | 
| 70 |  Hide softkeyboard  |  | 
| 71 |  Show softkeyboard  |  | 
| 72 |  Toggle Softkeyboard  |  | 
■ Physical keyboard
The terminal emulator can also control the input mode.
If you want to control the input mode from the physical keyboard, try setting "Preferences" → "Text input mode" → "IME shortcuts" appropriately.
■ Android Shortcuts
| Layout switch    |  [Ctrl]+[Space]   |  If multiple layouts are available.  | 
| Language switch  |  [Shift]+[Space]  |  If IME can use multiple languages.  | 
| IME switch       |  [Meta]+[Space]   |  If multiple IMEs are available.[Meta] means [Windows] key or [Command] key (Android 7 and up)  |